ReadIndex.md

ReadIndex() (type)

Data type handler for the index, [, builtin

Description

This is a function you would write when programming a Murex data-type.

It's called by the index, [, builtin.

The purpose of this function is to allow builtins to support sequential reads (where possible) and also create a standard interface for [ (index), thus allowing it to be data-type agnostic.

Usage

Registering your ReadIndex()

// To avoid data races, this should only happen inside func init()
lang.ReadIndexes[ /* your type name */ ] = /* your readIndex func */

Examples

Example ReadIndex() function:

package json

import (
	"github.com/lmorg/murex/lang"
	"github.com/lmorg/murex/utils/json"
)

func index(p *lang.Process, params []string) error {
	var jInterface interface{}

	b, err := p.Stdin.ReadAll()
	if err != nil {
		return err
	}

	err = json.Unmarshal(b, &jInterface)
	if err != nil {
		return err
	}

	marshaller := func(iface interface{}) ([]byte, error) {
		return json.Marshal(iface, p.Stdout.IsTTY())
	}

	return lang.IndexTemplateObject(p, params, &jInterface, marshaller)
}

Detail

While there is support for a dedicated ReadNotIndex() for instances of ![, the template APIs lang.IndexTemplateObject and lang.IndexTemplateTable are both agnostic to the bang prefix.

Parameters

1. *lang.Process: Process's runtime state. Typically expressed as the variable p
2. []string: slice of parameters used in [

See Also

• user-guide/Bang Prefix: Bang prefixing to reverse default actions
• parser/Get Nested Element ([[ Element ]]): Outputs an element from a nested structure
• apis/ReadArray() (type): Read from a data type one array element at a time
• apis/ReadArrayWithType() (type): Read from a data type one array element at a time and return the elements contents and data type
• apis/ReadNotIndex() (type): Data type handler for the bang-prefixed index, ![, builtin
• apis/WriteArray() (type): Write a data type, one array element at a time
• apis/lang.IndexTemplateObject() (template API): Returns element(s) from a data structure
• apis/lang.IndexTemplateTable() (template API): Returns element(s) from a table
• parser/index: Outputs an element from an array, map or table

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This document was generated from lang/stdio/interface_doc.yaml.